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    An Experimental Study on the Effects of Different Pendulum Damper Designs on Structural Behavior
    (Springer International Publishing Ag, 2023) Aydin, Ersin; Ozturk, Baki; Kebeli, Yunus Emre; Gultepe, Gorkem
    Pendulum dampers, which are the subject of this study, are a type of tuned mass damper (TMD). In general, TMDs are effective since they are designed according to the first mode behavior of the buildings. In this study, the effects of pendulum dampers on the structural behavior are investigated by performing vibration experiments on a 3-storey shear frame model with reduced dimensions. Harmonic loads are applied to the test models with and without pendulums on a one-way shaking table. Firstly, experiments without dampers were performed on the selected 3-storey reduced building model, and structural responses were found. The mass of pendulum dampers is chosen to be around 3% of the total mass of the structural model. One of the main aims of this study is to reveal the effects of the different placements of the dampers on the dynamic behavior. Accordingly, a single pendulum is independently placed on the top floor, the second floor, and finally on the first floor. In addition, experiments are carried out by establishing double damper models and then a triple damper model. By creating seven different damper models, the experiments are repeated under harmonic loads with different frequencies. Tests under a harmonic load equal to the first mode frequency of the undamped model reveal the behavior of the models in the resonant state. Experiments show that the pendulums used are highly effective in the resonance state. Some models with more than one damper have also been shown to be effective at reducing dynamic response.
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    COMPARISON OF NUMERICAL ANALYSIS OF A SINGLE-SPAN STEEL PROTOTYPE STRUCTURE AND A SCALE MODEL STRUCTURE UNDER THE EFFECT OF SEISMIC LOADS
    (Konya Teknik Univ, 2023) Kebeli, Yunus Emre; Teberik, Seyma; Aydin, Ersin; Celik, Fatih
    One of the biggest problems encountered in many experimental studies is examining a real- size structure in the field or in a laboratory environment. With today's technological opportunities, it is possible to experimentally examine a real-sized structure in the field or in a laboratory environment. However, to do this, the manufacture of a large, real-size structure, experimental setup and measuring devices are required, which are costly. For this reason, it is not always possible to reach such a laboratory environment. It is very difficult to experimentally examine large-scale structures both economically and in terms of time saving. In this context, in this study, a scaling factor (A) widely accepted in the literature was used to design a scaled model to represent a real- size structure. A=10 was used in this scaling approach. A real-size three-story single-span steel prototype building was scaled to a laboratory-scale model structure and analyzed digitally with the Sap2000 program. The natural period/frequency values of the real-size prototype structure and the scaled model modeled in the Sap2000 program were examined. Later, Time history analyzes were performed using real earthquake records from El Centro (1940), Kobe (1995) and Northridge (1994). While real earthquake records were used as they were in the analysis of the prototype structure, these real earthquake records were used by scaling them depending on the scaling factor A in the analysis of the scaled model. Subsequently, the digital analyzes of the prototype and scaled structure were compared by looking at the acceleration and displacement values of each floor. It was observed that the results were close to each other when scaled according to the scaling factor (A). This situation demonstrated the accuracy of the scaling rates applied within the scope of the study. Thus, it has been shown that a real-size structure can be scaled to a model in a laboratory environment with correct scaling methods and that this prototype structure can be analyzed with more economical and simple methods.
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    DESIGN OF VISCO-ELASTIC SUPPORTS FOR TIMOSHENKO CANTILEVER BEAMS
    (Konya Teknik Univ, 2023) Aydin, Ersin; Kebeli, Yunus Emre; Cetin, Huseyin; Ozturk, Baki
    The appropriate design of supports, upon which beams are usually placed as structural components in many engineering scenarios, has substantial significance in terms of both structural efficacy and cost factors. When beams experience various dynamic vibration effects, it is crucial to contemplate appropriate support systems that will effectively adapt to these vibrations. The present work investigates the most suitable support configuration for a cantilever beam, including viscoelastic supports across different vibration modes. Within this particular framework, a cantilever beam is simulated using beam finite elements. The beam is positioned on viscoelastic supports, which are represented by simple springs and damping elements. These supports are then included in the overall structural model. The equation of motion for the beam is first formulated in the temporal domain and then converted to the frequency domain via the use of the Fourier Transform. The basic equations used in the frequency domain are utilized to establish the dynamic characteristics of the beam by means of transfer functions. The determination of the ideal stiffness and damping coefficients of the viscoelastic components is achieved by minimizing the absolute acceleration at the free end of the beam. In order to minimize the objective function associated with acceleration, the nonlinear equations derived from Lagrange multipliers are solved using a gradient-based technique. The governing equations of the approach need partial derivatives with respect to design variables. Consequently, analytical derivative equations are formulated for both the stiffness and damping parameters. The present work introduces a concurrent optimization approach for both stiffness and damping. Passive constraints are established inside the optimization problem to impose restrictions on the lower and higher boundaries of the stiffness and damping coefficients. On the other hand, active constraints are used to ascertain the specific values of the overall stiffness and damping coefficients. The efficacy of the established approach in estimating the ideal spring and damping coefficients of viscoelastic supports and its ability to provide optimal support solutions for various vibration modes have been shown via comparative experiments with prior research.